1. Technical Field of the Invention
The present invention relates generally to electric generators and chagrining systems for vehicles. More particularly, the invention relates to an improved structure of a rectifier for an automotive alternator, which ensures reliable electrical connection of the rectifier with other devices.
2. Description of the Related Art
Conventional rectifiers for automotive alternators generally include a plurality of positive-side rectifying elements (for example, positive-side diodes), a positive-side heat sink, a plurality of negative-side rectifying elements (for example, negative-side diodes), a negative-side heat sink, and a terminal block.
The positive-side rectifying elements are so mounted to the positive-side heat sink that heat generated by operation of the positive-side rectifying elements is dissipated through the positive-side heat sink.
Similarly, the negative-side rectifying elements are so mounted to the negative-side heat sink that heat generated by operation of the negative-side rectifying elements is dissipated through the negative-side heat sink.
The terminal block retains therein electrical conductors that are connected to the positive-side and negative-side rectifying elements. The positive-side and negative-side rectifying elements and the electrical conductors together form a rectification circuit, by which an AC output from a three-phase stator winding of the automotive alternator is rectified.
In such a conventional rectifier 100, as shown in FIGS. 7A-7B, at least one of the positive-side and negative-side heat sinks 101 is connected with a terminal 102 of another electrical device (for example, a voltage regulator of the automotive alternator) through an engagement between a male threaded member and a female threaded member.
Specifically, according to a first conventional approach, the heat sink 101 may be configured to have, as shown in FIG. 7A and FIG. 8, a female threaded bore 103 formed therein, which engages with a male threaded member 104, thereby connecting the terminal 102 with the heat sink 101.
However, with such a configuration, as the temperature of the heat sink 101 increases due to heat generated by operation of the rectifying elements mounted thereto, the engagement between the female threaded bore 103 of the heat sink 101 and the male threaded member 104 will become loose. As a result, the male threaded member 104 can be detached from the female threaded bore 103 of the heat sink 101, thus disconnecting the terminal 102 from the heat sink 101.
It should be noted that electrical load of automotive alternators has significantly increased in recent years, and thus the male threaded member 104 has become easier to be detached from the female threaded bore 103 of the heat sink 101 with the above configuration.
As an alternative, according to a second conventional approach, the heat sink 101 may be configured to have, as shown in FIG. 7B, a through-bore 106 that is not threaded and permits a threaded portion of the male threaded member 104 to extend therethrough to engage with a female threaded member (i.e., a nut in FIG. 7B) 107. At the same time, the terminal block 105 may be configured to have a recessed portion 108 and extend to allow the female threaded member 107 to be accommodated in the recessed portion 108. Further, the recessed portion 108 of the terminal block 105 may be so shaped to keep the female threaded member 107 from rotating therein.
With such a configuration, it is possible to connect the terminal 102 with the heat sink 101 through the engagement between the male threaded member 104 and the female threaded member 107 while preventing the engagement from becoming loose due to heat generated by operation of the rectifying elements mounted to the heat sink 101. Moreover, it is also possible to securely retain the female threaded member 107 within the recessed portion 108 of the terminal block 105.
However, with the above configuration, the female threaded member 107 will receive a large torque when the male threaded member 104 is brought into engagement with the female threaded member 107 for connecting the terminal 102 to the heat sink 101 after assembly of the heat sink 101 with the terminal block 105. This torque will then be transmitted to the inner wall of the recessed portion 108 of the terminal block 105, which is generally made of a resin material, thus causing the terminal block 105 to be damaged.
In addition, Japanese Patent First Publication No. 2003-169457 discloses a rectifier for an automotive alternator, in which a metallic fixing bracket (or fitting) having a female threaded portion is provided in a resinous terminal block. The female threaded portion of the fixing bracket engages with a male threaded member to securely connect a heat sink to the terminal block, so as to reduce vibration of the heat sink that occurs during operation of the automotive alternator.
However, in the above rectifier, the fixing bracket will receive a large torque when the male threaded member is brought into engagement with the female threaded portion of the fixing bracket. Consequently, as in the case of FIG. 7B according to the second conventional approach, this torque will cause the resinous terminal block to be damaged.